1. Field of the Invention
The present invention is directed toward a method for controlling a vehicle heating, ventilation, and air conditioning (HVAC) system. In particular, the present invention relates to sensing a solar azimuth and instituting appropriate measures to effectively cool an interior of the vehicle.
2. Description of Related Art
In modern vehicles it is common to have an HVAC system for an occupant compartment (hereinafter “cabin”). The HVAC system provides warm and cool air to the cabin of the vehicle and allows occupants to select a set temperature for the cabin. Once the set temperature is selected, the HVAC system will provide conditioned air to adjust the climate of the cabin.
However, many factors can affect how comfortable the interior climate feels to the vehicle occupant. For example, sunlight entering the cabin may cause the occupant to feel too warm, even with the cabin temperature adjusted to the set temperature. In order to account for these and other factors, additional sensors are typically installed in the vehicle to provide feedback to a controller of the conditions inside and outside of the vehicle.
These sensors may include for example, an outside air temperature sensor, a cabin temperature sensor, and a solar sensor. The outside air and cabin temperature sensors measure outside air and cabin temperature, respectively, while the solar sensor measures solar azimuth. Solar azimuth is the horizontal rotation angle from Due South (in the Northern Hemisphere) or from Due North (in the Southern Hemisphere) of the sun and is usually measured in degrees. As the vehicle changes direction or course, the measured solar azimuth also changes.
Frequently updated signals from the outside air, cabin, and solar sensors are transmitted to the controller. The controller utilizes these signals to determine the appropriate action to take with the HVAC system so as to effectively warm or cool the cabin. For example, when the cabin temperature is elevated and the measured solar azimuth is small, the cabin is aggressively cooled by the HVAC system. However, when the cabin temperature is elevated, but the measured solar azimuth is large, the cabin would not be as aggressively cooled.
As the vehicle may be substantially heated by the sun during non-operation and then subsequently driven in a direction in which the measured solar azimuth is large, the HVAC system may under cool the cabin. The cabin is under-cooled because the HVAC system is being controlled based upon the current measured large solar azimuth that is sensed, and not the small solar azimuth that previously heated the vehicle.
Therefore, there exists a need in the art for a method to better control the HVAC system when the measured solar azimuth is large and the cabin temperature is elevated.